PROJECT SUMMARY The goal of this project is to characterize the effects of estrogen and its receptor - estrogen receptor 1 (ESR1) - on aqueous humor outflow, intraocular pressure, and risk for glaucoma development. Primary open-angle glaucoma (POAG), as the most common subtype of glaucoma, is characterized by retinal ganglion cell death, optic nerve degeneration, and progressive visual field loss without an identifiable cause. Elevated intraocular pressure (IOP) is the primary and only modifiable risk factor for POAG development. This pressure is regulated by the trabecular meshwork (TM) which modulates aqueous humor (AH) outflow. Previously, genome-wide association studies identified >122 IOP-associated genes. Our integrated bioinformatics analysis revealed that ESR1, also known as estrogen receptor ?, was at the center of a functional network of these IOP-associated genes, suggesting that it may play a role in IOP regulation. Several epidemiological studies have suggested that low estrogen levels may contribute to glaucoma risk due to a higher prevalence of POAG in males than females and a higher prevalence in post-menopausal females than pre-menopausal females or post-menopausal females undergoing hormone replacement therapy. Inversely, pregnancy, a high estrogen state, has been associated with lower IOP. In addition, it has been well-established that estrogen is protective for several ocular cell types, including retinal and corneal cells. However, the impact of estrogen on the TM has yet to be explored. Therefore, in this proposal, we hypothesize that moderate estrogen levels reduce IOP and POAG risk by promoting proper TM function through ESR1 transcriptional regulation of IOP and POAG related genes. We will test this hypothesis with the following aims. In Aim 1, in order to assess the effects of estrogen signaling on IOP and ocular health, we will measure IOP and conduct retinal optical coherence tomography (OCT) on male and female Esr1-/- mice and wild type female mice undergoing a bilateral oophorectomy. In Aim 2 we will determine the effects of estradiol, the active form of estrogen, on the transcriptional profile, morphology, and function of primary human TM cells using RNA-Seq and growth, contraction, and phagocytic assays. Successful completion of this project will improve our current understanding of the role of the TM in POAG pathogenesis, confirm low estrogen levels as a novel risk factor for high tension POAG, and identify novel therapeutic targets for this blinding illness.